fix: #3553342 Race condition in LocalTaskManager::getLocalTasks() with fibers

   */

  protected $account;

  /**

   * Flag that indicates if local tasks are currently being loaded.

   */

  protected bool $loadingLocalTasks = FALSE;

  /**

   * Constructs a \Drupal\Core\Menu\LocalTaskManager object.

   *

   * {@inheritdoc}

   */

  public function getLocalTasks($route_name, $level = 0) {

    if ($this->loadingLocalTasks && \Fiber::getCurrent() !== NULL) {

      // Primary and secondary task are rendered in separate blocks, each within

      // their own fiber. Both call this method for a different level, but the

      // data is built for both levels on the first call. If the first call

      // gets suspended, for example due to an entity load in a URL access

      // check, the second block will then call into this. If the data is

      // already being built, and we're in a fiber, suspend once to allow the

      // first fiber to complete building the data. If it is still not done,

      // proceed anyway, which may build that information twice but will not

      // return incomplete local task data.

      \Fiber::suspend();

    }

    if (!isset($this->taskData[$route_name])) {

      $this->loadingLocalTasks = TRUE;

      $cacheability = new CacheableMetadata();

      $cacheability->addCacheContexts(['route']);

      // Look for route-based tabs.

      $this->taskData[$route_name] = [

        'tabs' => [],

        'cacheability' => $cacheability,

      ];

      // Look for route-based tabs.

      if (!$this->requestStack->getCurrentRequest()->attributes->has('exception')) {

        // Safe to build tasks only when no exceptions raised.

        $data = [];

        foreach ($local_tasks as $tab_level => $items) {

          $data[$tab_level] = empty($data[$tab_level]) ? $items : array_merge($data[$tab_level], $items);

        }

        $this->taskData[$route_name]['tabs'] = $data;

        $this->taskData[$route_name] = [

          'tabs' => $data,

          'cacheability' => $cacheability,

        ];

        // Allow modules to alter local tasks.

        $this->moduleHandler->alter('menu_local_tasks', $this->taskData[$route_name], $route_name, $cacheability);

        $this->taskData[$route_name]['cacheability'] = $cacheability;

      }

      else {

        $this->taskData[$route_name] = [

          'tabs' => [],

          'cacheability' => $cacheability,

        ];

      }

      $this->loadingLocalTasks = FALSE;

    }

    if (isset($this->taskData[$route_name]['tabs'][$level])) {

    $this->assertEqualsCanonicalizing(['context.example1', 'context.example2', 'route', 'user.permissions'], $cacheability->getCacheContexts());

  }

  /**

   * Test multiple parallel calls with fibers.

   */

  public function testGetTasksBuildWithFibers(): void {

    $definitions = $this->getLocalTaskFixtures();

    $this->pluginDiscovery->expects($this->once())

      ->method('getDefinitions')

      ->willReturn($definitions);

    $active_plugin_id = 'menu_local_task_test_tasks_view';

    $map = [];

    foreach ($definitions as $plugin_id => $info) {

      $mock = $this->prophesize(LocalTaskInterface::class);

      $mock->willImplement(CacheableDependencyInterface::class);

      $mock->getRouteName()->willReturn($info['route_name']);

      $mock->getTitle()->willReturn($info['title']);

      $mock->getRouteParameters(Argument::cetera())->willReturn([]);

      $mock->getOptions(Argument::cetera())->willReturn([]);

      $mock->getActive()->willReturn($plugin_id === $active_plugin_id);

      $mock->getWeight()->willReturn($info['weight'] ?? 0);

      $mock->getCacheContexts()->willReturn([]);

      $mock->getCacheTags()->willReturn([]);

      $mock->getCacheMaxAge()->willReturn(Cache::PERMANENT);

      $map[] = [$info['id'], [], $mock->reveal()];

    }

    // Simulate an access callback that suspends a fiber.

    $this->accessManager->expects($this->any())

      ->method('checkNamedRoute')

      ->willReturnCallback(function (string $route_name) {

        if ($route_name === 'menu_local_task_test_tasks_edit') {

          \Fiber::suspend();

        }

        return AccessResult::allowed();

      });

    $this->factory->expects($this->any())

      ->method('createInstance')

      ->willReturnMap($map);

    $this->setupLocalTaskManager();

    $this->argumentResolver->expects($this->any())

      ->method('getArguments')

      ->willReturn([]);

    $this->routeMatch->expects($this->any())

      ->method('getRouteName')

      ->willReturn('menu_local_task_test_tasks_view');

    $this->routeMatch->expects($this->any())

      ->method('getRawParameters')

      ->willReturn(new InputBag());

    $first_fiber = new \Fiber(fn () => $this->manager->getLocalTasks('menu_local_task_test_tasks_view', 0));

    $second_fiber = new \Fiber(fn () => $this->manager->getLocalTasks('menu_local_task_test_tasks_view', 1));

    $fibers = [$first_fiber, $second_fiber];

    $suspended = FALSE;

    do {

      foreach ($fibers as $key => $fiber) {

        if (!$fiber->isStarted()) {

          $fiber->start();

        }

        elseif ($fiber->isSuspended()) {

          $suspended = TRUE;

          $fiber->resume();

        }

        elseif ($fiber->isTerminated()) {

          unset($fibers[$key]);

        }

      }

    } while (!empty($fibers));

    // Ensure that the fibers were suspended at least once to make sure that

    // the expected scenario is tested here.

    $this->assertTrue($suspended);

    // Assert that both fibers return the correct result.

    $this->assertEquals([

      'menu_local_task_test_tasks_settings',

      'menu_local_task_test_tasks_edit',

      'menu_local_task_test_tasks_view.tab',

    ], array_keys($first_fiber->getReturn()['tabs']));

    $this->assertEquals(['menu_local_task_test_tasks_view_child1', 'menu_local_task_test_tasks_view_child2'], array_keys($second_fiber->getReturn()['tabs']));

  }

  protected function setupFactoryAndLocalTaskPlugins(array $definitions, $active_plugin_id): void {

    $map = [];

    $access_manager_map = [];